Browsing by Author "Haladuick, Shane"

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    A contribution to risk-based inspection and maintenance planning for deteriorating pipelines and pressure vessels
    (2017) Haladuick, Shane; Dann, Markus R; Maes, Marc; Achari, Gopal; Egberts, Philip; Huang, Qindan
    Engineering systems are subject to deterioration processes, such as corrosion and fatigue, which reduce the resistance to failure. If failure occurs, it can have large social, economic, and environmental consequences. To mitigate this risk, regular inspections and maintenance are performed. To minimize the overall cost of operating the system, it is important to optimize the inspection and maintenance plan. Lifecycle risk-based inspection and maintenance planning, which involves determining the expected total cost of operating a system over its lifecycle, is the most established method of determining the optimal inspection and maintenance plan. However, lifecycle risk-based inspection and maintenance planning for complex engineering systems with many components requires a detailed analysis that can be computationally demanding; therefore, simplifications and assumptions are commonly used in the literature. The objective of this dissertation is to expand the state of knowledge in risk-based inspection and maintenance planning for pipelines and pressure vessels, removing many common assumptions and simplifications. Some aspects of the research specifically target pipelines or pressure vessels, while others are generic to any engineering system. Specifically regarding pressure vessels, a simple methodology is presented to determine the optimal maintenance time for a pressure vessel with an unexpectedly severe defect. This methodology is then expanded to account for the dependent failure events in pressure vessels with multiple defects and failure modes. For pipelines, a risk-based maintenance methodology is developed to decide whether it is better to continuously repair defects in a pipeline or to replace entire pipeline sections. This methodology also examines the impact of an uncertain lifecycle on risk-based maintenance planning. For general engineering systems, the use of heuristic algorithms in improving the computational efficiency of solving risk-based inspection and maintenance optimization problems is examined. Finally, a methodology is developed to perform risk-based inspection planning for the next inspection type, without requiring a lifecycle analysis. This study aids system operators in determining the optimal inspection and maintenance plan. It also provides methodology to perform risk-based inspection and maintenance planning in a computationally efficient or simpler manner, to make the techniques more practically applicable.
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    Relating field observations and snowpack tests to snow avalanche danger
    (2014-09-23) Haladuick, Shane; Jamieson, Bruce
    The avalanche forecast regions in Canada range from 100 to 50,000, far larger than the 10 km2 covered in a typical backcountry day. This difference in scale could cause the local avalanche danger to differ from the regional bulletin. This study assessed the relationship of field observations and snowpack tests with the local avalanche danger. Data were collected over 6 winters during 425 field days. Univariate and multivariate cross-validated classification trees were created using the observations to predict the local danger. The univariate trees show the critical value of an observation that indicates elevated danger. The multivariate trees show how the observations can be combined. These trees provide objective data that could form the framework of a decision support tool to help recreationists localize the danger. Contrary to popular belief, field observations were more valuable than stability tests for localizing the danger.